Data from: Quantifying effects of environmental and geographical factors on patterns of genetic differentiation

Elucidating the factors influencing genetic differentiation is an
important task in biology, and the relative contribution from natural
selection and genetic drift has long been debated. In this study, we used
a regression-based approach to simultaneously estimate the quantitative
contributions of environmental adaptation and isolation by distance on
genetic variation in Boechera stricta, a wild relative of Arabidopsis.
Patterns of discrete and continuous genetic differentiation coexist within
this species. For the discrete differentiation between two major genetic
groups, environment has larger contribution than geography, and we also
identified a significant environment-by-geography interaction effect.
Elsewhere in the species range, we found a latitudinal cline of genetic
variation reflecting only isolation by distance. To further confirm the
effect of environmental selection on genetic divergence, we identified the
specific environmental variables predicting local genotypes in allopatric
and sympatric regions. Water availability was identified as the possible
cause of differential local adaptation in both geographic regions,
confirming the role of environmental adaptation in driving and maintaining
genetic differentiation between the two major genetic groups. In addition,
the environment-by-geography interaction is further confirmed by the
finding that water availability is represented by different environmental
factors in the allopatric and sympatric regions. In conclusion, this study
found that geographical and environmental factors together created
stronger and more discrete genetic differentiation than isolation by
distance alone, which only produced a gradual, clinal pattern of genetic
variation. These findings emphasize the importance of environmental
selection in shaping patterns of species-wide genetic variation in the
natural environment.